Hemopoiesis

HAEMOPOIESIS
Means formation of the blood cells which include RBC, WBC
(Granulocytes and Agranulocytes) and platelets.
Blood is a special type of fluid connective tissue. It is an opaque fluid
and it is red in colour due to presence of haemoglobin.
Physical Properties :
Colour : Arterial blood is scarlet red and venous blood is purple.
Volume : volume of blood is a normal adult is 5 litres.
Reaction and pH : It is slightly alkaline and its pH is 7.4.
Specific Gravity : Specific gravity of total blood is 1.052 – 1.061.
Specific gravity of blood cells : 1.092 to 1.101.
Specific gravity of plasma : 1.022 to 1.026
Viscosity : Blood is 5 times more viscous than water. It is mainly due to RBC
and plasma proteins.
Composition of Blood
Plasma Proteins (55%) Blood Cells (Formed Elements) (45)
Organic Inorganic RBC WBC Platelets
Substances Substances
Lymphocytes Agranulocytes
- Neutrophils - Lymphocytes
- Basophils - Small
- Eosinophils - Large
- Monocytes
Plasma :
It has around 91% - 92% of H2O and 8 – 9% of solid organic substances.
1) Proteins (albumin), Globulin and Fibrinogen), 2) Carbohydrates (Glucose),
3) Facts, 4) No protein nitrogenous substances (NH3 amino acids, creatine, uric
acid etc), 5) Internal secretions (hormones), 6) Enzymes and 7) Antibodies.
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Inorganic Substances :
1) Calcium
2) Sodium
3) Potassium
4) Magnesium
5) Chloride
6) Iodide
7) Iron
8) Phosphates
9) Copper
Functions of Blood :
1) Nutrient function : It helps in absorption of nutritive substances like
glucose, A.A., lipids and vitamins from GIT and carried to different
parts of body.
2) Respiratory function : Transport of respiratory gases is done by blood O2
and CO2 are transported through blood.
3) Excretory function : Waste products due to various metastasis are
removed and carried to the excretory organs through this medium.
4) Transport of Hormones : Hormones and few enzymes are carried by
blood to different parts of body.
5) Regulation of H2O balance : H2O content of blood is freely
interchangeable with interstitial fluid which helps in regulation of water
content of body.
6) Acid base balance : Plasma proteins and Hb acts as buffers and helps in
regulation of A-base balance.
7) Regulation of body temperature : Due to high specific heat of blood,
helps in maintaining thermoregulatory mechanism.
8) Storage function : serves as a ready source of substance like water,
glucose, Na and K which are taken from blood during starvation and
fluid loss etc.
9) Defense functions : Due to various cells present in it.
Blood cells are basically divided into 3 categories ;
- Red blood cells
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- White blood cells
- Platelets
Red Blood Cells : They are circular, biconcave cell without a nucleus be
considered as a kind of a living bag containing Hb, RBC. Mainly carry oxygen
from lungs to the tissues.
White Blood Cells : They are basically divided into ;
i) Granulocytes
o Neutrophils
o Eosinophils
o Basophils
ii) Agranulocytes
o Monocyte
o Lymphocyte
i. Small
ii. Large
They are basically divided based on the presence or absence of granules
in the cells. They all are nucleated cells with granules or of granular. They are
mainly involved in the body’s defence mechanism against various bacteria and
even some foreign material.
Platelets :
They are small colourless, non-nucleated and moderately refractive
bodies. These formed elements of blood are considered to be the fragments of
cytoplasm. They are spherical / oval shaped and become oval shaped when
inactivated. Plates play key role in the reaction of hemostasis.
All the blood cells including lymphocytes, originate from a single class
of primitive cells, the pluripotent stem cell. But however lymphocytes differ
from other blood cells, which arise normally arise after fetal life only within the
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bone marrow and referred to as marrow cells. Lymphocytes although
originating from the marrow precursor cells, mature and proliferate outside of
the marrow in the thymus and peripheral lymphoid tissue.
Erythrocytes, neutrophils, eisinophils, monocytes and platelets have
finite life span and therefore fraction of these cells must be replaced daily.
Approximate concentration and Daily Production in Peripheral Blood Cells :
Mean concentration /
Microitre
Daily Production
Rate / Kg Body Wt.
Erythrocytes – Males
- Females
5.4 x 106
4.8 x 106
3.8 x 106
WBC - Neutrophils
- Monocytes
- Basophils
- Eosinophils
- Lymphocytes
4,500
300
40
150
2500
1.6 x 109
1.7 x 108
-
Variable
-
Platelets 2.5 x 106
2.8 x 109
In addition to this bone marrow must respond intermittently to increased
demands for specific cells like Eg.Granulocyte to tight bacterial infection or for
erythrocytes after acute blood loss.
HAEMOPOIETIC ORGANS:
During embryogenesis (Development of fetus),the site of haeamopoiesis
changes for several times. The first blood cells which is formed i.e. the
nucleated erythrocyte appear in the blood islands in Yolk sac and “these yolk
sac” heamopoiesis is produced during early development i.e. 3rd
week – 34d
month gestation period (IUL). The embryonic erythrocytes (yolk sac derived)
do not loose their nuclei during maturation and they contain heamoglobin
molecules of α and β family which are different from those founding later
fetal / adult erythrocytes.
As the fetus develops, the organic formation takes place. This stage that
is during the mid-gestation period the main organ for heamopoiesis is fetal
liver. Even the spleen also participates in the formation. During this period β-
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chains of heam are present which are different from the adult β-globin chains
of heamoglobin.
During, about 20th
embryonic week, heamopoiesis begins in bone
marrow. It is fully active in RBM by 7-8th
month of fetal life. As fetus matures
heamopoiesis increases in the RBM and decreases in the liver and spleen. At
birth practically whole of bony skeleton contains active marrow. After birth all
blood cells except lymphocytes are generally made in RBM.
Bone marrow is supplied by nutrient arteries which widely branch into
capillaries which in turn enter sinuses and sinusoids. Between the sinuses and
sinusoids the stem cells and precursors cells which by process of multiplication
and differentiation form the erythrocytes, granulocytes and platelets. Only
once they are matured they enter the circulation through the apertures in sinus
walls.
Sites :
In young children, active heamopoietic marrow is found throughout both
the axial skeleton (cranium ribs, vertebra and pelvis) and the bone of
extremities. But in adults heamopoietic marrow is confirmed to axial skeleton
and proximal end of femur and humors.
In an adult heamopoietic marrow, it normally consist of islands of
cellular active marrow separated and supported by fat. In old age, proportion
of active marrow decreases and thereby fat increases.
In some pathological conditions like heamolytic anaemias,
thalassaemias, the marrow cellular activity increases at the expense of fat and
sometimes cellular changes also takes place. In certain rare pathological
conditions like myeloidmetaplasia, the heamopoietic activity runs back to
extramedullary sites like spleen and liver.
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GROWTH FACTORS :
These are cytokines which control growth, differentiation and function
of blood cells. Several different growth factors exist each capable of supporting
a particular spectrum of hemopoietic cell types. Physiochemically they are
acid glycoproteins which define these ability to alter growth and function of
progenitor cells and differentiated cells. These heamopoietic growth factor are
present in tissue fluids and blood in concentration of 10-10
to 10-11
. they effect
the target cells through binding to specific cell surface receptors.
Growth factors has 2 types of actions :
1) Induction of cell growth and differentiation in immature cells.
2) Modulation of effector functions in mature cells.
Some growth factors act synergistically and multiple growth factor act
simultaneously upon the precursor cells.
Macrophage play a central role in controlling heamopoiesis through
secretion of cytokine, IL-1.
IL-1 stimulation growth of T-lymphocytes with elevates IL3 , and stem
fibroblasts, endothelial cells to secrete GM-CSF and G-CSF. IL3 and GMCSF
inturn stem, early cell division of progenitors of most, if not all the myeloid cell
lineages. IL1- also acts upon mature blood cells, stimulation of release of
neutrophils from RBM.
IL3 acts upon myeloid cell progenitors along with GM-CSF. It acts
particularly on earlier progenitor cell subset expanding and preparing for
subsequent exposure to GM-CSF.
GM-CSF 1st
record to its ability to stimulate growth of gran, macrocytes
and eosinophils. They also stimulate early division of erythrocyte progenitor
and megakaryocytic progenitors. It also acts on mature granulocytes and
macrophages including enhancement of granulocyte responses to chemotactic
stimuli and ability of macrophages to kill intracellularly.
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For full development such factors (IL3 and GMCSF) are not enough,
but also simultaneous / sequential presence of 2nd
growth factor acting
specifically on more differentiated precursors.
For neutrophilic gram  it is Ci-CSF
Erythrocytes  Erythropoietin
In addition to growth factor a variety of humoral agents have been
identified that inhibit myeloid cell growth. They include TGF (transforming
growth factor), granulocytic protein lactoferrin, acidic isoferritius (certain
intracellular iron storage proteins) and Esthetics prostaglandins.
Growth Stages Growth Factors
1) Factors that act on
multilineage progenitors.
2) Granulocyte and macrophage
growth factor
3) Differentiation of neutrophils,
monocytes and eosinophils
4) Megakaryocyte growth factor
5) β – Lymhocytes
6) Erythroid cells
GM-CSF, G-CSF, CSF-1, IL-3,
4,6,11,12
GM-CSF (monocytes and
granulocytes)
G-CSF, CSF-1, IL-5
CFU-MK, IL-3, IL-6
CFU-Pre B, IL-7
BFU-B, CFU-E, IGF-1, IL-3
Heamopoietic Stem Cells :
They can be said as “stem cells represent a cell type which, in adult
organic can maintain its non numbers in spite of physiological / artificial
removal of cells from the population.
Means “maintaining its own number”.
They possess found props.
i) An ability by cell division to give rise to new stem cell (self
renewal).
ii) An ability to different mature specialized blood cells.
- Frequency of in bone marrow established : 1-2 /1000 nucleic stem cells
and small number also circulate in blood.
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- Specific supporting tissues like bone marrow (man) permit growth and
differentiation of stem cells and they are referred as “heamopoetic
microenvironment”.
- When multitude of cells arises from a single cell, or when a single stem
cell gives rise to a spleen colony that multitude of cells is called a
CLONE.
- In normal heamopoesis, mature blood cells originate from multiple stem
cells, so normal heamophoisis is polyclonal.
- In hematological malignancies, the progency of single abnormal stem
cell may overgrow and suppress normal stem cells and here
heamopoiesis is monoclonal.
- As the stem cells differentiations, it losses its ability to give rise to all
blood cells and becomes committed to production of one / more cell
lines. Different mechanism have been postulated to regenerate
commitment.
a) Probability of differentiation increases with each division of a
stem cells.
b) Extra cellular inductive factor perhaps the heamopoetic growth
factor / cell surface molecules in the heamopoietic
microenvironment determine the changes within a stem cell that
leads to commitment
c) Others says, due to some series of unknown factors influence the
probabilities for self renewal / commitment.
It is said that, functionally 3 different stem cells.
a) Pluriopotent stem cell
b) Myeloid stem cell (which gives rise to erythrocytes, granulocytes of all
types, monocytes and platelets0.
c) Lymphocytes stem cells.
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- As commitment progress, the capability of the stem cells for self
renewal diminishes and when it is markedly limited / lost, the cell is no
longer called a stem cell but called as PROGENITOR CELL.
- This progenitor cell are recognized by their ability to give rise to clonal
aggregates colonies) of differentiated cells on cultures.
- Progenitor cells are more numerous than stem cells and like stem cells
present in both bone marrow and circulating blood.
Blast Cells :
- The immediate offsprings of progenitor cells are the blast cells. For the
erythroid series, there are blast cells like the pronormoblasts, early,
intermediate and late normoblasts.
- In case of granulocytic series, they are the myeloblasts and similarly
there are lymphoblasts, monoblasts and megakaryoblasts.
- Blast cells are immature cells.
Stages of Development :
Except for 1st
3 months of fetal life, all erythroid development are
extravascular. When erythroids cells is almost mature, it enter the sinusoids
from the extravascular space.
The most primitive cell is called the pluripotent stem cell. This cell
divides and differentiates, whereas the pluripotent stem cell can give rise to
erythrocytes, granulocyte, monocyte, lymphocyte, platelet, that is why it is
called pluripotent stem cell (Pluripotent – Capable of producing many /
different cells). But the daughter cells are not capable of producing all the
types of cells they can produce either ;
- Myeloid series
- Erythroid series
More they advance in lineage, more they become restricted in the
plurality of the patency.
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The pluripotent stem cells divides and differentiated to give rise to
committed stem cell. Here there are two types, one type of committed stem
cells gives rise to myeloid series (Gram, no, RBC, platelets) but not
lymphocytes. Whereas other type of committed stem cell gives rise to
lymphocyte (T and B).
Cells committed to produce myeloid series now divide and differentiate
to produce the daughter cells called “Progenitor cells’. Several type of
progenitor cells develop. One type of PC gives rise to cells of erythroid series,
another granulocyte. Monotype and other megakaryocyte, and last eosinophil.
Progenitor cells are usually called “Colony Units” (CFU) and designated
as CFU-E, CFU, CFU-EO, CFU-Mega.
RBC : There are 2 P.C.
a) BFU-E b) CFU-E
From CFU-0 : Pronomoblast cell (1st
cell in the which is
morphologically recognizable cell in erythro series) develops. Nucleus is
strongly basophilic which very scanty cytoplasm and no Hb found. From
pronormoblast  early neuroblast – also called change basophilic neuroblast
 intermediate / chromatophilic normoblast  late normoblast ortho
chromatic normoblast.
Hb appears in intermediate normoblast and so but poly chromatophilic
and nucleus becomes smaller. In late neuroblast plenty of cytoplasm which is
eosinophilic with fair amount of Hb, nucleus very small and deep pyknotic.
Late Normoblast : Reticulocyte (matures for ½ in RBM and then enters
peripheral blood, where it not a still a fully matured RBC Then it matures from
mature RBC.
Nucleus becomes smaller as cell matures from pronormo to late
normoblast and here the pyknotic nucleus is extend to form reticulocyte.
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As cell mature s- more and abundant cytoplasm.
Hb-appears in intermediate normoblast and develops.
Cell is capable of division to intermediate normoblastic. After this stage
only maturation no division.
PRODUCTION OF MYELOID CELL LINES :
ERYTHROPOIESIS :
Erythroid Progenitor Cells (EPC) :
The EPC are of 2 types ;
Burst forming Units – Erythrocyte (BFU-E)
Colony forming units – Erythrocyte (CFU-E)
- BFU-E are large, multilobulated colonies whereas the CFU-E are much
smaller colonies.
- Actually the BFU-E gave rise to CFU-E through continuum of
intermediate forms and it is a most differentiated erythroid progenitors.
- Growth of BFU-E requires presence of one / more growth factors which
are collectively refer to as Burst Promoting Activity (BPA) which is
general present in IL-3 and GM-CSF.
- In contrast CFU-E is independent of BPA but require hormone
erythropoietin for proliferation and maturation to heamoglobin
containing erythrocytes.
- Neither BFU-E nor CFU-E have morphological features permitting their
distinction from each other or their recognition as members of erythroid
series.
MATURATION OF NORMOBLASTS :
- The earliest morphologically recognizable member of erythroid series is
the Pronormoblast / erythroblast.
- This appears as cell of moderate – large size with a round nucleus
occupying most of the cell and containing fine punctuate chromatin and
blue nucleoli and with a rim of cytoplasm which is deeply basophilic.
The deep blue colour of the immature cells is due to the presence of
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large amounts of RNA and which is associated with active protein
synthesis.
- Subsequently as the cell matures the nuclei become smaller and denser,
losing their nucleoli and then cell is then called normoblast and
subsequently the size of normoblast diminishes progressively, the
nucleus shrinks into a purple black pyknotic mass that is finally
extended. Any remaining nuclear material is very effectively removed
by a process of pitting during passage through the splenic sinus walls
and eventually the nuclei become pyknotic and structureless before
being extruded from the cell after which they are phagocytosed.
- The cytoplasm also matures, the dense blue colour gradually changes
through intermediate shade to orange pink as increasing amount of
hemoglobin are synthesized.
- The successive cytoplasmic change from blue to orange pink, various
adjectives are given as – Basophilic, Polychromatic, Orthochromatic.
- 3-5 cell divisions takesplace during pronormoblast- normoblast
maturation.
- Others are pronormoblast gives rise to form 8-32 RBC cell division
stops at the late normoblast stage.
- The normal time required for an erythroid cell to mature from a
pronormoblast to a newly released circulating RBC is generally 5-7
days.
- Heamoglobin synthesis has 3 requisites.
a) Adequate amounts of mRNA for polypeptide chains of globin.
b) Cell must synthesize normal amounts of tetrpyrole porphyrin.
c) Iron must be available for incorporation into protoporphyrin to
form HEME.
Plasma transferring brings the iron to the developing erythroid cells.
- When lack of body iron prevents transferring from bringing sufficient
iron to developing RBC’s for heamoglobin synthesis erythropoiesis is
impaired leading anaemiabesis.
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MATURATION OF RETICULOCYTE :
When first formed by extrusion of nucleus of the late normoblast, a non
nucleated RBC which is larger than the mature RBC and does not yet have its
full complement of heamoglobin but still possess some cytoplasmic RNA,
mitochondria and surface transferring receptors i.e. the synthetic machinery
required to continue to make heamoglobin.
This newly differentiated immature RBC is called as reticulocytes,
which is named because the staining procedures show the cells residual RNA,
giving rise to beads and strands of dark blue material that form reticulin
network within cytoplasm.
Reticulocyte normally matures for 1-2 days before entering the
circulation, during which time heamoglobin synthesis continues and the cells
size decreases.
Regulation and Assessment of Erythropoiesis :
Although the growth factors with BPA may help in the earliest stage of
erythropoiesis, the ERYTHROPOIETIN functions as a major regulate of
erythropoiesis.
ERYTHROPOIETIN :
This is produced by the cells of the kidney that sense tissue hypoxia.
This tissue hypoxia may result from any of the 3 cases.
i) Decreased blood hemoglobin content (Anaemia)
ii) Failure to oxygenate Hb adequately in the lungs (lung disease,
certain congenital heart diseases, high attitude).
iii) Impaired release of O2 from Hb at a normal tissue O2 tension
(as occurs when blood C.O. level is elevated).
- Normal erythropoiesis requires a basal level of stimulation of erythroid
progenitor cells by erythropoietin.
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Factors Influencing Erythropoiesis :
1) Erythropoietin
2) BPA – For proliferation of BFU-E
3) Vitamins – B12, folic acids important other like Vitamin B6 and C
4) Iron – Required for Hb synthesis
5) Miscellaneous
Life Span and Destruction :
Total life span is 120 days.
As age advances, the enzymes which protect the erythrocyte from
damaging effects of O2 begin to loose their efficiency. Therefore oxidative
damages begin to appear and RBC, becomes rather rigid, spheroidal and
fragile.
During circulation, RBC pass through spleen whose diameters are very
narrow and when such fragile RBC pass through these, they are ruptured. But
young and healthy RBC with sufficient degree of biconcavity can survive.
Normally spleen is the important slaughter house for RBCs, but when
erythemia are diseased, fragility increases, they break down when passing
through other structures also particularly liver.
Functions of RBC :
1) RBC mainly help in carrying of the oxygen from the lungs to the
peripheries.
2) It also helps in carrying CO2 from the peripheries to the lungs. The
haemoglobin in the RBC combines which CO2 and form carbheamoglobin.
About 30% of CO2 is transported in this form.
3) Hb in RBC also function as a good buffer by this action, it regulates the H+
ion concentration and thereby takes part in the maintenance of the acid-
base balance.
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4) RBC carry the blood group antigens like A.agglutinogenous,
B.agglutinogen and Rh factor which helps in determination of blood group.
- In end stage kidney disease / after bilateral nephrectomy, the basal
secretion of erythropoietin is eliminated, patients become severely
anaemic unless they are infused with exogenous recombinant
erythropoietin. In chronic steady state anemia’s, the plasma Hb
concentration rises in inverse proportion to degree of reduction of blood
haemoglobin concentration.
- When erythropoietin secretion is increased, CFU-E and their more
mature progency increase in number.
- Total marrow cellularity and relative proportion of erythroid precursors
to granulocytic forms are augmented. Reticulocytes are released without
first maturing in the marrow.
- The reticulocyte count will be elevated, reflecting both an elevated rate
of RBC production and persistence for a longer period n the circulating
blood of reticulocytes released early from the marrow.
Erythropoiesis Count :
- Total erythropotsis – estimated from the number of nucleated RBC in
bone marrow.
- Effective erythropoiesis – erythropoiesis producing RBC’s that circulate
which can be estimated from the absolute reticulocyte count correlated
for the early release of marrow reticulocytes.
- In effective erythropoiesis – erythropoiesis which gives rise to defective
cells that do not circulate but are phagocytosed by macrophages within
the marrow. This can be evaluated by comparing the number of
nucleated RBCs seen in marrow with the corrected, absolute reticulocyte
counts.
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- In healthy persons only negligible fraction of erythropoiesis is
ineffective, but in certain disorders of erythorpoiesis, like pernicious
anaemia, in effective erythropoiesis may predominate.
- When erythropoiesis is stem by erythropoesis and large amounts of iron
for Hb synthesis are readily available from the breakdown of RBC’s, s
occurs in most heamolytic disorders, effective erythropoiesis may
increase 6-8 fold.
- Whereas erythropoiesis stem by erythropoiesis, but only limited
amounts of iron are readily available from normal body stores like in
acute blood loss, effective erythropoesis increases only about 2-3 fold.
LEUKOPOIESIS :
- It is defined as development and maturation of leukocytes.
- The leukocytes are of 2 main varieties based on their presence of
granules.
i) Those with granules – Granulocytes – 2 types
a) One with multi lobed nuclei - Polymorphonuclear
leukocytes 9Eosonophils, Basophils, Neutrophils).
b) Other has a single sound / lobulated nucleic monocytes.
ii) The non granular leukocytes – lymphocytes.
Formation / Leukopoiesis :
The bone marrow and blood contains progenitor cells that give rise to
colonies of granulocytes macrophages or both. The progenitor cells cannot be
distinguished morphologically from other undifferentiated marrow and blood
cells.
The earliest morphologically identifiable member of granulocyte series
is he myeloblast. It has a large sound nucues containing fine stippled
chromatin and from 1-5 nucleoli, cytoplasm bulue and of any granules.
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As the cell matures is nucleus undergoes condensation and finally regeneration.
It cytoplasm acquires 3 types of granules – large azurophilic primary granules
(appropriate), Two types of granules called specifies tertiary granules.
NEUTROPHIL :
They are generally found in peripheral blood, bone marrow and even in
tissues. So it is said that neutrophils are present in 3 pools.
a) Bone marrow pool 90% of neutralization
b) Pool of peripheral blood 3% - Actual circulation and Marginal pool.
c) Tissue pool 7%
Formation :
The red bone marrow pool - - Mitotic Pool and Post-mitotic pool
- In mitotic pool – neutrophil are dividing as well as maturing (3-5 days)
and it consists of myeloblasts, promylocytes and myelocytes. In post
mitotic pool – cells no longer divided but only mature.
- The committed stem cells in the myeloid series are the main cells which
divide and differentiate to form different colony forming units which
later give rise to different blood cells.
- The progenitor cells for neutrophils being the CFU-GM which gives rise
to both granulocytes or neutrophil and monocyte.
- The CFU GM undergoes gradual change to form myeloblast which is
the precursor of neutrophil.
- Myeloblast divides and matures to promyelocyte and this and divides
and matures to form myelocyte.
- Till here the division takes place in the mitotic pol. From myeloblast
myelocyte it takes -3 – 4 days.
- The myelocyte enters the post mitotic pool where only matures but not
divides and is converted to the neutrophil. This takes about 6 days in
post mitotic pool.
- In short journey of neutrophil from birth to grave.
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- Myeloblast  Myelocyte  Neutrophil  entry into intra vascular pool
(6-7 hours)  Emigration into tissue pool (1-4 days)  Death.
- Total life span from the stage of myeloblast which is a recognizable
state is 12-14 days.
- The most primitive cell as the CFU-GM : it is a common ancestor for
both neutrophil and monocyte. But it is not recognizable.
- CFU-GM divides and differentiates to myeloblast which is the first cell
(precursor) of neutrophil which can be identified by the microscope.
Nucleus is large, contains many nuclei and cytoplasm takes the bluish
stain and contains no granules.
- Myeloblast matures further and become promyelocyte where there is
only one nucleolus in nuclei and the cytoplasm contain primary granules
(azurophilicgram).
- Promyelocyte develops to myelocyte which has radish nucleus with
some indentation and abundant cytoplasm and cytoplasm contains pink
staining granules (here primary granules no longer visible) no nucleolus.
- Next stage of development is metamyelocyte where the nucleus shows
indentation and cytoplasm contains large number of secondary granules.
- Metamyelocytes matures to form band cell where the indentation in
nucleus further deeps and acquires almost a horse shoe shape.
- Finally the nucleus is segmented and becomes lobed. Uptill this stage it
was in bone marrow now it is released into circulation by forming young
neutrophil.
Factors Influencing :
i) Colony stimulating factor : Required for growth of CFU-GM.
Produced by mononuclear cells
ii) Prostaglandin-E : Inhibits CFU-GM (inhibit check mechanism (feed
back much) by which excess CSF activity is prevented.
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iii) Acidic lactoferrin : Produced by monocytes. Inhibits the normal
CFU GM columns in both marrow but not the leukemic ones.
iv) Lacrtoferrin : Produced by granules of neutrophils in whites CFU
GM.
- The life span is shortened example, in acute infections the immature
forms (i.e. even metamyelocytes) are released into blood to meet
demands of excessive needs of neutrophils.
- The normal bone marrow reserve for neutrophil is 3 days and for
children it is more less. Most neutrophil which are destured to die enter
GIT where they die and are excreted out.
EOSINOPHIL :
- These are also present in different pools like neutrophils i.e.
i) Bone marrow pool – 5.5 days
ii) Intravascular pool : 8-12 hours
 Circulatory
 Marginal
iii) Tissue pool – Death
- Eosin are born and matured in RBM where their total stay is about 5.5
days. Then they enter the circulation i.e. the intra vascular pool and stay
for about 8-12 hours. Sizes in the marginal and the actual circulatory
pool is they are almost equal. From the circulatory pool they migrate to
the tissues where they die.
Formation :
- Origin and development of eosinophil is similar to that of the neutrophil.
- The most primitive cell for eosin is CFU-EO which cannot be identified
by microscopic method forms myeloblast.
- The myeloblast (more specific eosinophilic myeloblast) matures to form
eosinophilic myelocyte.
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- This further matures to form the meta myelocyte and then finally the
mature eosinophil.
- This is released into the peripheral blood.
Factors effecting the Origin /Development / Release :
i) CSF  Required for growth of CFU-E.
ii) Eosinopoitin : Increases the eosinophil count in the peripheral blood.
Especially when there is eosinopenia.
iii) Parasitic invasions and allergic conditions causes rise of eosiniophil
count.
iv) Cortisol : Causes eosinopenia (fall of eosinophil count).
Eosinophil (Matureform) :
- The mature eosinophil contains bilobed nucleus and distinctive large
granules which stains orange red.
- Material called Major Basic Protein (MBP) and make sup 50% of large
granule has a key role to play in the eosinophils ability to damage the
larva tissue stage.
- 50% of large granule has a key role to play in the eosinophil’s ability to
damage the larva issue stage of heliminthic parasite and is extremely
potent tissue toxin.
- A potent bactericidal and tissue toxin called (a) Eosinophilic cationic
protein (ECP), (b) a neurotoxic protein and (c) Eosinophilic peroxidase
are also present in large granules.
- Along with these it also contain Aryl Sulphatase enzyme which
hydrolyses the S-O ester linkages and which can inactive the sulfur
containing leukotrienes that tissue mast cells liberate in immediate
hypersensitivity.
- For these reasons the blood eosinophils, increased count rise in
helminthic infestations and in allergic states. Even when blood
eosinophil counts are normal eosinophils are usually increase din
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number at tissue sites of allergic reactions, whereby degrading mast
cells thereby decreasing the clinical mean of allergic responses.
- Administration of adrenal lucocorticoids causes blood eosinophil levels
to fall within about 2 hours, presumably because of marignation and
sequestration of the circulating cells. Continued administration leads to
eosinopenia and impaired release of eosinophils from bone marrow.
Functions :
- They have antibacterial function due to MPO granules.
- It has anti parasitic roles – act against the larva of the parasites. This is
due to presence of MBP.
- It also helps in allergic reaction.
BASOPHIL :
- They constitute around 1% of total WBC’s
- The basophiles of blood develop in the ed bone marrow
- The basophils have a very closed relation to the mast cells, but it is
exactly not known.
- Basophils are produced by RBM and present within the blood but
whereas the must cells are present outside the circulation / blood within
the tissue, that are produced in the RBM.
- The functions of both being some due to same constitution and same
morphology.
The Development :
The development stages of basophil are basically same as that of he
other granulocytes.
- The first cell which can be secondary is the blast cell.
- This differentiate and divides to form promyelocyte. This again divides
and differentiates from myelocyte.
- This myelocyte differentiates to form the metamyelocyte.
- The granules being to appear in the myelocyte stage.
21

- The meta myelocytes mature to form into a band cell.
- This band cell matures fully to form a basophil.
- This basophil is released into the blood where they stay for couple of
hours and then migrate into the tissues.
- After this what happens is unknown.
Mature Basophil :
Diameter varies from 10-12 µ. Nucleus is irregular and often ‘S’
shaped. Cytoplasmic granules are coarse and basophil and often so present or
the nuclear zone that the nucleus appears partly covered by the granules.
The granules of basophil (its counterpart in the tissue mast cell) contain
1) Histamine, 2) Heparin, 3) Acid peptides, 4) Acid hydrolases, 5) Neutral
proteolytic enzyme.
Functions :
1. It reacts in the allergic conditions.
2. It has an antibacterial effect.
3. It also helps in phagocytosing of the foreign cells, i.e. it
acts as a defence mechanism in various conditions.
MONOCYTES :
- They constitute around 2% - 8% of total WBC and the target of the
WBC’s (12-20 µ).
- like other WBCs it is also distributed into different pols of the body.
i) Marrow pool
ii) Intravascular pool – 8-71 hours
iii) Tissue pool – RES
- There is a controversy regarding the marginal pool whether it is
present /not. Some say its size is over 3 times of the circulatory pool
and some say it is totally absent.
Development
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- The most primary cell being the CFU-GM as said earlier and cannot be
identified by the staining procedure.
- This differentiates to form promonocyte which can be identified and
which has nucleus rounded/ slightly indented and cyto deeply basophilic
and contains very few granules.
- This promonocyte differentiates to form the monocyte. Uptil here the
development occur sin RBM.
- Monocyte is released into blood circulation where it stays for some time
(exactly not known).
- It enters the tissue and becomes tissue macrophage and member of RES.
Here it undergoes further differentiation in tissues to give rise to cells of
the mononuclear phagocyte system. Tissue macrophage.
- Life span of it is unknown.
Mature Monocyte / macrophage :
- Nucleus not lobed, commonly ovoid and very often indented, the
indentation is so deep than it acquires a horse shoe shaped appearance.
- Although it is categorized as anon granulocyte the cytoplasm yet
contains very fine granules.
Functions :
i) Formation of tissue macrophage : main function is to remove various
undesirable substances by phagocytosis in various tissues like liver,
spleen, lungs and so forth.
ii) Role in acute and chronic infection: In any site of infection,
neutrophils emigrate and phagocytose them, therefore in first 24
hours bacterial invasion neutrophils preponderate, whereas after that
monocytes emigrate and attack them but no granules are present in
them, but digest by production of H2O2.
Neutrophils – 1st
line of defence
Monocyte s- 2nd
line of defence
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In chronic infection, macrophage engulf the bacteria but does not kill
them / digest which is seen typically in incubation period of typhoid
fever.
iii) Role in lymphocyte mediated immunity : In this macrophages
produces monokines which causes death of invading antigen and
well as innocent host cells.
iv) Monocytes produce – CSP, prostaglandin and acid lactoferrin to
control production of neutrophils.
LYMPHOCYTES :
- This constitutes around 25-30% of the WBC, the lymphocytes play an
important role in immunity. Functionally these lymphocytes are
classified into 2 types – T.lymphocytes and B.lymphocytes. T-
lymphocytes respective for cellular immunity. B lymphocytes – respect
for humoral immunity.
Development :
- The development starts in the bone marrow directly from the stem cells.
- The pluripotent stem cell gives origin to the CFU and lymphoid STEM
CELLS (LSC).
- In the RBC the most primitive cells is the pluripotent stem cell, which
gives rise to committed tem cells. One type of CSC give rise to cells of
myeloid series (erythrocytes, granulocytes, monocytes and platelets) and
other type gives rise to lymphocytes (either B/T lymphocytes).
Pluripotent stem cells  Committed stem cells  Myeloid series and
Lymphoid series.
Formation of T.lymphocytes :
- From the RBM the committed stem cells of lymphocyte migrate to
cortex of the thymus where they greatly proliferate in number by mitotic
division.
- From cortex of thymus these newly formed cells go to the medulla of
thymus where no further divisions take place.
24

- In medulla of cortex they undergo further processing and after such
processing they become immunologically competent T.cells and now
they are released into circulation.
FORMATION OF β-LYMPHOCYTES :
- The committed stem cells (committed to produce β-lymphocytes)
migrate to bursa of fabricus (in humans the homologous organ for this
being lymphoid tissues of gut. Eg. Tonsils, Payers patches of intestine
and appendix and they are collectively known as gut associated
lymphoid tissue (GALT) and nowadays they say that homologous to it is
the RBM) where they are further processed and after rule processing the
mature β-lymphocytes are released into the circulation.
- Thymus and Bursa Fabricus (GALT and RBM) are termed the central
lymphoid tissue.
- From the central lymphoid tissue, the immunologically competent T-
cells and B cells come out and enter the peripheral blood, stay for couple
of hours in the blood and later enter the peripheral lymphoid tissue.
- In primary lymph tissue they stay for couple of hour sand come and
again come back to the peripheral blood and from where it again goes
back to peripheral lymphoid tissue thereby making, back and forth
shutting between blood and peripheral lymphoid tissue.
- The life span of lymphocytes is variable, some have unusually long life
span (yes together).
- While these lymphnodes are staining lymphnode, if the person is
suddenly challenged by antigen, the lymphocytes become lymphoblast
and multiply vigorously with the lymphnodes.
- Thymus regresses in adult life and in old age it regresses remarkably.
However T-lymph continue to multiply within lymph nodes (Peripheral
25

lymphoid tissue) and T.lymphocytes can increase eve in old age when
necessity arises.
- In case of RBC, development occurs only in RBM in the post natal life.
Btu for lymphocytes, these reside in the lymph nodes and help in
development. Lymphocytes belong to different clones when an invasion
occurs by specific antigen, members of specific clone undergo blast
transformation and proliferation. Ti is in this way, the lymphocyte
supply to the peripheral blood is maintained.
- Therefore the deepening of bone marrow in adult life, the absolute count
of lymphocytes count in peripheral blood should not fall, although that
of WBC’s belonging to myeloid series should fall.
- It also explains that although thymus regresses and becomes atrophied in
adult life, the supply of lymphocytes to the peripheral blood is not
hampered.
- But if thymus development is poor in the et al stage, the T.lymphocytes
do not develop and child dies early.
Functions :
- They helping the specific immunity of the body, removes the various
antigen like bacteria / virus / tumor cells.
- Tissues when transplanted to our body from foreign persons are usually
rejected and this phenomenon is called as tissue rejection. This
mechanism specifically plays a vital role in tissue rejection of the cancer
tissue.
- NK and K cells kill cancer cells.
PLATELET / THROMOCYTE :
There are three types of formed elements of which thrombocytes are the
one which assists in hemostasis (prevention of blood loss) by various processes
including the helping in the coagulation.
Normal platelet count is between 150,000 – 400,000/cmm. When the
count goes below 1,00,000 – thrombocytopenia is diagnosed and when it goes
26

below 40,000 hemorrhagic manifestations occurs. Thus 40,000 platelet count
is called the critical count.
Development :
- Platelets are derived from the giant cells in RBM i.e. megakaryocytes,
whose diameter is usually around 100 µm.
- A single megakaryocyte can give rise to about 1000 platelets. The
platelets are produced in the RBM. The most primitive cell in line of
platelet production as usual is the pluripotent stem cells.
- This stem cell divides and differentiates to CFU megakaryocyte, which
gives rise to promegakaryoblast (small sized cell).
- The promegakarblast matures to form a megakaryobalst which inturns
matures to from mega keraocyte.
- They are readily recognizable by heir large size, multi lobulated nucleus,
abundant cytoplasm.
- Normal marrow contains about 1 megakal/500 nucleated red blood cells.
- Analysis of DNA content of megakaryoblasts suggest that they contain
even number of multipliers of the normal human DNA content
(Polyploidy) Zn, Gn, 8n etc. This results from nuclear duplication of
cell division, a process called entoreduplication.
- The pseudopods of megakaryocyte are thrown inside of the sinusoids of
bone marrow and then the tip of the pseudopoid is detached; this
detached part of pseudopoid which does not contain any nucleus become
a platelet.
- A single megakaryocyte can give rise to about 1000 platelets and after
this, the remnant of megakaryocytic is attached by the macrophages of
the bone marrow, engulfed and digested.
- Normally bone marrow contains only about one days reserve of
platelets. Therefore human begins are susceptible to develop
thrombocytopenia more quickly than granulocytopenia/
erythrocytopenia.
27

Morphology :
- Platelets are very small borders consisting of cytoplasm encased within
a membrane. They are non nucleated structures.
- When inactive state i.e. circulating in blood they have disc like structure
but when there is an injury/ bleeding they become activated and have a
spherical structure.
- Platelets contain mitochondria and golgi apparatus and apart from these
some special structures like granules, tubules, filamentous structures
made of actinomycin and various chemicals like adrenalin, serotonin,
ADP and thrombospondin. The platelet does not contain DNA / RNA.
Factors Influencing Thrombopoisis :
i) Thrombopoietin : Substances which stimulates thrombopoiesis.
ii) TGFβ : Released from α granules of platelets and cause deepening
of platelet count by suppressing (-ve feed back mechanism).
Functions of Platelets :
- When here is any injury to blood vessels, these platelets adhere (to
injured site), to aggregate (large number adhere to one another) and
release many chemicals and pulp in hemostatic plug formation.
- Platelets and release adrenaline and serotonin, thus helping in the
vasoconstriction (which is necessary for hemostasis).
- They also release some chemicals which help the blood to coagulate
and they are called or coagulants.
- They contain actinomyosin which helps in contraction and retraction of
the platelet plug.
- They also help in fixation of fibrin and platelets so that ultimately clot
formation occur sonly where there is platelet plug.
- They also release some substances which oppose the hemostasis and
blood coagulation.
Life Span :
28

- Normal life span is about 7-12 days.
- Most of platelets are destroyed in spleen. About 1/3rd
of platelet reside
in spleen. Therefore spleenectomy causes a rise in blood platelet count.
Applied Physiology:
- Thrombocytopenia – condition where platelet count is low which leads
to purpura but not coagulation defect.
- After surgical operation and child birth number of platelets increase this
produces risk of intravascular clotting and to prevent this early
ambulation is advocated.
CLINICAL CONSIDERATIONS :
Anaemias : means deficiency of RBCs which can be caused ;
1) Too rapid blood loss
2) Too slow production of RBCs
Types :
a) Blood loss anaemia  To rapid loss of blood – Acute and Chronic.
b) A plastic anemaia : Lack of bone marrow functioning, which may be
due to
- Gamma ray radiation
- Excessive x-ray exposure
- Certain industrial chemicals
- Drugs
c) Megaloblastic anaemia : Loss of any of these i.e. vitamin B12, folic acid,
zinc and intrinsic factor.
d) Hemolytic anaemias : Due to early destruction / excessive destruction of
RBCs anaemia occurs.
- Hereditary spherocytosis  Cells are small and spherical, so they can’t
compress themselves when they pass through spleen, so easily rupture.
29

e) Sickle cell anaemia : Due to abnormal shape of Hb, cells becomes
elongated and thereby fragile and rupture easily.
Thalassaemias – Very little hb is present (which is due to deficiency)
cells are abnormal in shape and fragile.
Erythroblasts fetalis – Rh (+)ve antibodies of fetus are attached by
Rh(-)ve mother and leads to destruction of RBC’s and severe anaemia.
Effect of Viscosity :
Normally the viscosity of blood is 3 times that of water, due to anaemia,
it falls around 1.5 times that of H2O. So this decreases the resistance to blood
flow in peripheral vessels, so that greater quantities of blood return to heart.
Moreover hypoxia due to diminished transport of O2 by blood causes the tissue
vessels to dilate, allowing further increase in return of blood to heart. So one
of the major effects of anaemia is greatly increased work load on heart.
POLYCYTHEMIA :
When tissues become hypoxic due to little O2 in atmosphere (high
altitudes, etc) the blood forming organs produce large quantities of RBC’s.
This is physiological polycythemia. Here increases upto 6-8 mil/cm3
Polycythemia Vera : RBC as high as 7-8 mil/m3
and hematocrit increases as
high as 60-70%.
- It is a tumours condition of organs that produce blood cells.
- Also causes excess production of WBCs and platelets.
- Here total blood volume increases by 2 times which results in entire
vascular system engorged and many capillaries become plugged by
viscous blood, because the viscosity increases by 10 times to that of
H2O.
DENTAL MANAGEMENT :
In patients with G-6-PD deficiency where there is hemolysis due to
alteration of cell membrane and thereby fragile and leading to rupture of cells.
30

Blockage of Hexose monophosphate shunt path way in individuals with G-6-
PD deficiency allows accumulation of oxidans in RBCs. These substances
which generally produce wet hb and denatured Hb forms Heinz bodies which
attach to cell membranes thereby altering the cell membranes which leads to
hemolysis of cells.
Such patients have increased incidence of drug sensitivity with
sulfonamides, aspirin and chloremphenicol, penicillin, streptomycin and
isoniazid etc. Drugs containing phenacetin is avoided in these patients.
Sickle Cell anaemias :
- Arrange short appointments
- Avoid long and complicated procedures
- Maintain good dental repair
- Institute aggressive preventive dental care
a) Oral hygiene instruction
b) Diet control
c) Tooth brushing and flossing
d) Fluoride gel application
- Avoid oral infection; treatment aggressively when present
- Use L.A. (avoid G.A.) / epinephrine for routine dental care and for
surgical procedures use 1:1,00,000 epinephrine in LA.
- Avoid Barbiturates and strong narcotics; sedation with Diazepam can be
used.
- Use prophylactic antibiotics for surgical procedures.
- Avoid liberal use of salicylates. Pain control with acetaminophen and
codeine.
- Use N2O – O2 with great care.
WBC :
1) Agranulocytosis : Where bone marrow stops producing WBC’s leaving body
unprotected agonist bacteria and other agents which invade body.
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General human body lives in symbosis with many bacteria and all
mucous membranes of body are constantly exposed to large number of
bacterial, i.e. mouth, GIT, eyes, urethra and vagina. Therefore any decrease in
number of WBC imm. Allows invasion. So within 2 days after RBM stops
producing WBCs, ulcers appear in mouth and colon and develops respiratory
infection. Bacteria from these enter surrounding tissues and invade the body
and blood. Treatment death often ensues 3-6 days after acute agranulocytosis
begins.
Due to irradiation of γ-rays/exposure to drugs and chemical (benzene /
anthracene) cause aplasia of RBM. So after irradiation injury where all stem
cells and other cells are destroyed in RBM, sufficient time should be given for
the regeneration to occur before doing any dental treatment.
DENTAL MANAGEMENT OF LEUKEMIC PATIENT :
New dental patients under medical treatment for leukemias, lymphoma
and multiple myeloma must be identified by their health history and current
status established by consultation with the physician.
Patient who is in a state of remission can receive mot indicated dental
treatment. Patient with acute signs and symptoms of disease should receive
only cons. Emergency dental care until infection has been received and patient
has returned to normal state.
Patient with advanced disease and when prognosis is limited as in many
cases of acute leukemia and multiple myeloma, should receive only emergency
care, complex restorative procedure and extensive dental restorations are
usually not indicated. If any procedure is to be done a platelet count / bleeding
time should be obtained and if abnormal platelet replacement is indicated.
For recently diagnosed leukemic patient dentist should be involved early
on during the treatment planning stages of cancer therapy. For example, in
32

addition to providing oral prophylaxis and hygiene instrument he may
recommend RCT /extension of teeth susceptible to acute exacerbations.
CONCLUSION :
As good as the saying “if it weren’t for the rocks in its bed the stream
would have no song’. So likewise if no heamopoiesis, there is no formation of
blood, as blood is the medium of life.
33

Hemopoiesis

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Hemopoiesis